Vista Wireless Connection Failed

Hi, I just got a new laptop and I'm having some problems connection to a
wireless network. I can connect to other networks without a problem, but one
security enabled network will not let me connect. My old machine with XP
connects without a hitch, no input whatsoever. The error that it gives me is
along the lines of "network denied the assocation..."

Is there anything I can do to connect without having to access the router
etc? Why can XP access and not Vista?

Thanks